1. Field of Invention
The present invention relates to a valve lift device. More particularly, the present invention relates to a variable valve lift apparatus that variably controls a lift amount of a valve opening/closing an intake port or an exhaust port of an internal combustion engine in multi steps.
2. Description of Related Art
An internal combustion engine generates power by burning fuel in a combustion chamber in an air media that is drawn into the chamber. Intake valves are operated by a camshaft in order to take in the air, and the air is drawn into the combustion chamber while the intake valves are open. In addition, exhaust valves are operated by the camshaft, and a combustion gas is exhausted from the combustion chamber while the exhaust valves are open.
An optimal operation of the intake valves and the exhaust valves depends on a rotation speed of the engine. That is, optimal opening/closing timing of the valves or an optimal lift depends on the rotation speed of the engine.
In order to achieve such an optimal valve operation depending on the rotation speed of the engine, research has been undertaken on a variable valve lift (VVL) apparatus that enables different valve lifts depending on the engine speed.
Meanwhile, a rocker arm is disposed on a rocker arm shaft, a cam that is disposed at one side of the rocker arm is used to lift a valve that is disposed at the other side of the rocker arm, a structure/method variably controlling the lift amount of the valve has been researched, and particularly a variable valve lift apparatus that has a simple structure and is easily assembled has been being researched.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.